Electric switch.



No. 710,455. Patented Oct. 7, I902.

a. u. HILL.

ELECTRIC SWITCH.

(Application filed Aug 10, 1901.

(In Model.)

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UNITED STATES PATENT OFFICE.

GEORGE H. HILL, OF GLENRIDGE, NElV JERSEY, ASSIGNOR TO SPRAGUE ELECTRIC COMPANY, OF NElV YORK, N. Y., A CORPORATION OF NEW JERSEY.

ELECTRIC SWITCH.

SPECIFICATION forming part of Letters Patent N0. 710,455, dated October 7, 1902.

Application filed August 10, 1901. Serial No. 71,640. (No model.)

To all whom, it ntrty concern:

Be it known that I, GEORGE I-I. HILL, a citizen of the United States of America, and a resident of Glenridge, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Electric Switches, of which the following is a specification.

This invention relates to electric switches, and particularly to switches of the cylinder type in which spider-castings on the shaft are insulated therefrom by an insulating compound. Heretofore the segments or castings have been painted after they have been assembled on the shaft in such way that whenever dust, oil, and dirt accumulated on the surface of the com pound between the castings aleak or current occurred between them. In a short time a heavy arc would form, with the consequent burning out of the switch. Also as the coat of paint furnishes a film or skin over dissimilar substances-namely, the castings and the compound-it is apt to crack, and thus give opportunity for an initial leak.

The object of the present invention is to so improve the insulation as that thesedefects are avoided; and the invention consists of certain novel features to be hereinafter described in detail and then claimed.

In the accompanying drawings, Figure 1 is a side elevation of so much of a switch constructed in accordance with the present inventionassufficestoillustratethe same. Fig. 2 is a section on line 2 20f Fig. 1,the brushes being omitted; and Fig. 3 is a section on line 3 3 of Fig. 1.

The shaft or spindle A of the-switch, here shown as of the cylinder type, is covered with an insulating compound B, so as to form a layer under and between the castings or segments O, the lugs C of which carry the copper contacts D. The brushes are lettered D. The well-known way of applying the insulating compound and castings to the shaft is to string a number of rings of suitable insulating compound upon the shaft and then set and hold the castings thereupon, so that they will not change their relative position to each other. This having been done the parts are subjected to heat, as by gas-jets, so as to soften up the rings of insulating compound and make them plastic. Other rings are forced on the shaft so as to squeeze the softened and now plastic material up into theinterstices between the castings, and the process is continued until all of the interstices are filled with the com pound, when the structure is allowed to cool off, and the exposed surfaces of the insulation and the castings are then covered with a coat or coats of paint.

In the present invention the described method of assembling is also preferably used, but before assembling the castings O are enameled 'ur japanned with some suitable insulating material E-such as porcelain, for instance. This enamel or japan is hard and baked on the castings,.so that it will resist the subsequent heating when the insulating compound is applied to the shaft. The enamel or japan also provides a hard insulating-skin on the castings, which is not readily broken down, and thus prevents the initial leak between the castings, and consequently the disastrous arcing which follows. A coat of paint F may or may not be applied to the exposed surfaces of the insulation and castings, as heretofore, shown in Figs. 2 and 3.

The painting of the castings after they have been assembled upon the shaft is not as advantageous as previous enameling or japanning, for the reasons that the paint cannot be hard-baked on account of the low temperature limit of the insulating compound, and is therefore not as durable, and also that the paint is liable to crack.

What I claim as new, and desire to secure by Letters Patent, is-

1. An electric switch, comprising a shaft, a body of insulation on the shaft, and contactsupports embedded in the said insulatingbody and'each having a skin or film of suitableinsulating material separate and distinct from, and wholly separating the supports 2 memes themselves from, the said insulating-body, tinct and separate from any coating on the substantially as described. insulation, substantially as described. 10 2. An electric switch, comprising a shaft, Signed by me, at New York, this 6th day of contact-supports having on their inner por- August, 1901. tions adjacent to the shaft a skin or film of suitable insulting material, and insulation between the supports and between the supports and shaft, such skin or fillll being dis- I GEORGE H. HILL. Witnesses:

EDWARD J. MURPHY, SAMUEL W. BALCH. 

